Chinese herbal medicine for post-viral fatigue: A systematic review of randomized controlled trials

Background Fatigue is a common symptom after viral infection. Chinese herbal medicine (CHM) is thought to be a potential effective intervention in relieving fatigue. Purpose To assess the effectiveness and safety of CHM for the treatment of post-viral fatigue. Study design Systematic review and meta-analysis of randomized controlled trials (RCTs). Methods The protocol of this systematic review was registered on PROSPERO (CRD42022380356). Trials reported changes of fatigue symptom, which compared CHM to no treatment, placebo or drugs, were included. Six electronic databases and three clinical trial registration platforms were searched from inception to November 2023. Literature screening, data extraction, and risk bias assessment were independently carried out by two reviewers. Quality of the included trials was evaluated using Cochrane risk of bias tool, and the certainty of the evidence was evaluated using GRADE. The meta-analysis was performed using Review Manager 5.4, mean difference (MD) and its 95% confidence interval (CI) was used for estimate effect of continuous data. Heterogeneity among trials was assessed through I2 value. Results Overall, nineteen studies with 1921 patients were included. Results of individual trial or meta-analysis showed that CHM was better than no treatment (MD = -0.80 scores, 95%CI -1.43 to -0.17 scores, P = 0.01, 60 participants, 1 trial), placebo (MD = -1.90 scores, 95%CI -2.38 to -1.42 scores, P<0.00001, 184 participants, 1 trial), placebo on basis of rehabilitation therapy (MD = -14.90 scores, 95%CI -24.53 to -5.27 scores, P = 0.02, 118 participants, 1 trial) or drugs (MD = -0.38 scores, 95%CI -0.48 to -0.27 scores, I2 = 0%, P<0.00001, 498 participants, 4 trials) on relieving fatigue symptoms assessing by Traditional Chinese Medicine fatigue scores. Trials compared CHM plus drugs to drugs alone also showed better effect of combination therapy (average MD = -0.56 scores). In addition, CHM may improve the percentage of CD4 T lymphocytes and reduce the level of serum IL-6 (MD = -14.64 scores, 95%CI 18.36 to -10.91 scores, I2 = 0%, P<0.00001, 146 participants, 2 trials). Conclusion Current systematic review found that the participation of CHM can improve the symptoms of post-viral fatigue and some immune indicators. However, the safety of CHM remains unknown and large sample, high quality multicenter RCTs are still needed in the future.


Introduction
Fatigue is a subjective uncomfortable feeling symptom, which lacks a unified definition.Patients describe fatigue as a persistent overwhelming feeling of tiredness, severe lethargy, or lack of energy, physical weakness, and cognitive decline [1].As a common non-specific symptom [2], fatigue can be the main patients' complaint or the accompanying symptom of a variety diseases.Some fatigue can be relieved soon through adequate rest or treatment, while many fatigues cannot be relieved and may last for a long time, causing harm to people's psychology and physiology, seriously interfering with people's life [3].
There are many reasons for fatigue, among which more and more evidence shows that viral infection, such as Epstein-Barr virus, Bernard virus, human herpes virus, cytomegalovirus, etc, is related to fatigue [4].After infection, some people will leave fatigue symptoms of long time and repeated attacks but the specific mechanism is still unclear.In addition, human immunodeficiency virus (HIV), hepatitis B virus and other infections often cause long-term fatigue symptoms of infected people.The results of AIDS and hepatitis B with large sample study in China show that the prevalence rate is up to 40% [5,6] and even more than 60% in England and North America [7,8], which cannot be alleviated after the application of antiviral drugs [9,10].In recent years, with the prevalence of COVID-19, people pay more attention to the symptoms and complications after acute viral infection, which are called "Long COVID", including symptoms of long-term fatigue [11].An meta-analysis have shown that approximately a third of individuals experienced persistent fatigue 12 or more weeks following confirmed COVID-19 diagnosis [12].The chronic fatigue after the virus infection not only leads to the emergence of anxiety, depression, and serious decline in the quality of life [13], but also increases the economic burden of the whole society [14].
At present, treatment of fatigue is mainly symptomatic.Among them, drug therapy mainly includes antidepressants, vitamin or other nutritional therapies to improve clinical symptoms.Non drug therapy includes cognitive behavioral therapy and exercise therapy to relieve patients' anxiety, depression and other negative emotions [15], but it cannot fundamentally solve the problem and has not achieved satisfactory results [16].
According to the theory of Traditional Chinese Medicine (TCM), the disease mechanism of long-term fatigue is the deficiency in origin and excess in superficiality, due to excessive exertion, improper diet, internal emotional injury or exogenous pathogenic factors (e.g.viral infection) causing the deficiency of Qi, blood, Yin or Yang, then mixing with fire, phlegm and blood stasis [17].Among them, the healthy Qi of the human body is the key factor [18].TCM therapies, including Chinese herbal medicine (CHM), acupuncture, massage, Qigong and other non-pharmaceutical treatments, can play a complementary role in the treatment of chronic fatigue [19,20].CHM can help tonifying Qi and blood, regulating Yin and Yang, supplying deficiency and expelling excess, which is widely used in China [21].
At present, although there is no direct evidence for the usage rate of CHM in the treatment of post-viral fatigue, but in the past few decades, it has been widely used in clinic and achieved certain results in the treatment of cancer-related fatigue (CRF) and chronic fatigue syndrome (CFS).Evidence suggests that CHM can clearly decreased 1.77 scores in fatigue scale-14  scores as an adjuvant or monotherapy for CFS [22] and significantly lowered 1.47 scores in Brief Fatigue Inventory (BFI) global score for CRF [23].Meanwhile take Ginseng for example [24], up to now, various clinical practice and animal-based experiments have already confirmed the safe anti-fatigue effects of Ginseng Radix et Rhizoma, as well as its components.Ginseng Radix et Rhizoma is currently prescribed in the formula for Long COVID treatment as a monarch drug.Among these formulas, Qingjin Yiqi granules can significantly alleviate fatigue and have been recommended by the Rehabilitati on Guidelines of Integrated Medicine for Long COVID treatment in clinical.
Currently, there are two systematic reviews published in Pubmed evaluated the efficacy of interventions for post-viral fatigue, the interventions included mixed-methods [25] (e.g.exercise, psychological/behavioral, dietary, acupuncture or yoga) and Vitamin C [26].There is no evidence of evaluated the efficacy of CHM in the treatment of fatigue after viral infection.Therefore, this review aims to comprehensively search and critical appraisal all relevant randomized controlled trials (RCT) to explore the effectiveness and safety of CHM for the treatment of post-viral fatigue.

Methods
This review was reported according to PRISMA statement (S1 Appendix).The protocol of this systematic review was registered on PROSPERO, which is available on https://www.crd.york.ac.uk/prospero/display_record.php?ID=CRD42022380356 (CRD42022380356).

Eligibility criteria
We focused on post-viral fatigue, thus, those fatigue caused by mental illness (e.g.depression, anxiety disorders), cancer, anemia, endocrine disorders or chronic somatic diseases were not included.
We included studies if they met the following criteria: 1. Parallel-group RCTs with or without blinding method.Only the first phase data of randomized cross-over trials were included to avoid any carry-over effects.
2. Participants of any age across all regions and ethnicity, that had mild or above fatigue symptom assessed by validated instruments which had clear fatigue classification as a result of viral infection (The diagnosis is confirmed by pathogenic examination).At the same time, patients were enrolled with clear TCM diagnosis in line with the category of deficiency syndrome (including Qi deficiency, blood deficiency, Yin deficiency and Yang deficiency).
3. The intervention was oral administration of CHM, dosage form, dosage and composition of the prescription were not limited.
4. The control group was no treatment, placebo or anti-fatigue drugs.CHM combined with other treatments compared to other treatments alone were also included.
5. The primary outcome was fatigue symptom evaluation via score or fatigue scale (e.g.Chalder fatigue scale [27]), symptom disappearance rate and disappearance time.The secondary outcomes included quality of life measured by validated instruments (e.g.chronic liver disease questionnaire, CLDQ [28]), laboratory characteristics on immunerelated indicators (e.g.CD4 +, CD8+), pathogen related outcome indicators (e.g.HbsAg, Hbv DNA) and adverse events.
Exclusion criteria: 1. Incomplete data or full text not available

Information sources
We searched six electronic databases and three clinical trial registration platforms, including

Selection process
Citation of the retrieved literature exported from 6 electronic databases and three clinical trial registration platforms, and was imported into NoteExpress software to preliminary exclude the duplicates.Titles, abstracts and full text screened by two reviewers (Hu LY and Cai AQ) independently according to the eligibility criteria.Disagreements resolved by the third author (Cao HJ).

Data collection
Two authors (Hu LY and Cai AQ) independently extracted data form all eligible articles into a data extraction form.The conflicts resolved through discussion and consultation with a third author (Cao HJ).We extracted the following information for each trial:

Methodological quality assessment
The quality of the included trials was assessed using the Cochrane Collaboration's "Risk of bias (RoB) 2.0" tool [29] by two authors (Hu LY and Cai AQ).Three types of results were obtained: "low risk," "high risk," and "some concerns."The evaluation included randomization process, deviations from intended interventions, missing outcome data, measurement of the outcome, and selection of the reported result.

Data analysis
All statistical analysis was performed using Review Manager (Revman 5.4,The Cochrane Collaboration) software.Data was summarized using risk ratio (RR) with its 95% confidence interval (CI) for binary outcomes or mean difference (MD) with 95% (CI) for continuous outcomes.Statistical heterogeneity among included trials was evaluated by the I 2 value.Metaanalysis was conducted if there was no significant clinical (in term of difference of participants, intervention, control and outcomes) and statistical heterogeneity (I 2 <75%) among included trials.Considering the complexity of the herbal formula, random effects model was used in meta-analysis, pooling analysis was not be used if there was significant statistical heterogeneity (I 2 �75%) among trials and the source of heterogeneity could not be interpret by subgroup analysis.The funnel plot was used to explore the possibility of small study effects or publication bias, if there were ten or more studies in an analysis.

Sensitivity analysis and subgroup analysis
We implemented sensitivity analyses to explore the impacts of evidence quality on the robustness of review conclusions.Subgroups were classified by types of viral infection, patients' age (<18 years, �18 years), treatment principle (e.g.benefiting Qi, nourishing Yin, tonify Yang), level of fatigue symptom, duration of treatment (short-term is defined as less than or equal to 1 month, middle-term is 1-3 months, long-term is 3-6 months).

Evaluation on the certainty of the evidence
We evaluated the quality of evidence using GRADE (Grading of Recommendation, Assessment, Development, and Evaluation) [30].Evidence was rated as high, moderate, low, or very low according to study limitations, inconsistency, indirectness, imprecision, and possibility of publication bias.

Results
A preliminary literature search identified 3470 records, and 307 studies were screened out after deleting duplicates.

Risk of bias in studies
The risk of bias of the included trials was presented in Fig 2 .Most of the involved studies had large methodological deficiencies, only 1 study [32] was assessed as having low risk of bias and 1 study [31] was assessed as having some concerns, while the remaining trials were all evaluated as having high risk of bias (Fig 2).

Effectiveness of interventions
To explore the source of the heterogeneity among trials, we tried subgroup analysis according to the protocol, however, none of them can lower the I 2 value within groups.Thus, we did not report neither the results of meta-analysis when I 2 >75% nor the results of subgroup analysis.Funnel plot was not used since no meta-analysis with more than 10 included trials was conducted.Results of the included individual trials were shown in Tables 3 and 4 regarding to different outcomes.
Twelve trials [33,35,36,[38][39][40][41][43][44][45][46][47] compared CHM plus drugs to drugs alone, involving 1050 patients and three viral infectious diseases (viral hepatitis, HIV and viral myocarditis).All the studies reported the fatigue scores assessed through TCM syndrome scale.Higher scores indicated higher levels of fatigue.The results showed that, although 2 studies [29,35] found no difference between groups on increasing the fatigue scores, other ten trials all suggested that CHM combined with drugs had better effect than drugs alone in improving the fatigue symptom, however, due to the obvious heterogeneity among included trials, pooling analysis was not conducted for these twelve trials (Table 3).
Three studies [38,39,43] compared CHM plus drugs to drugs alone, which involving 399 patients and two viral infectious dieases (hepatitis B and viral myocarditis), reported both CD4 and CD8 T lymphocytes levels.The results showed that in terms of CD4 T lymphocytes levels, CHM combined antiviral therapy had better efficacy than antiviral therapy in increasing the percentage of CD4 T lymphocytes.However, there was no statistical difference in the reduction of CD8 T lymphocytes levels (Table 4).

TNF-α
Serum TNF-α levels was reported in two studies [35,39].The results showed that there was no statistical difference in reducing TNF-α comparing CHM plus drugs to drugs (Table 4).

Adverse events
Adverse effects were reported in four studies [31,32,41,46], mainly including diarrhea, nausea and vomiting, dizzy, somnolence, anemia, abnormal liver function, liver injury, excessive menstruation, nose bleeding and headache (see Table 5 for details).The remaining 15 trials did not report any adverse reactions.

GRADE assessment
Table 6 shows a summary of the overall quality of evidence assessment for the effect of CHM on the fatigue scores in different comparison.Certainty in the evidence was variable for CHM vs. no treatment (Very low), CHM vs. Placebo (Low), CHM vs. placebo on basis of rehabilitation therapy (Low), CHM vs. drugs (Very low), CHM plus drugs vs. drugs (Very low).All evidence were downgraded due to imprecision, other reasons for downgrading included high risk of the bias, obvious heterogeneity and probability of the publication bias (Table 6).

Summary of the main findings
This review found that CHM has good effect as adjuvant therapy or monotherapy for viral infectious diseases on improving post-viral fatigue.CHM may ameliorate patients' fatigue symptom, with an average lower of 0.56 points in TCM fatigue syndrome scale (CHM vs. Drugs 0.38 scores lower; CHM plus drugs vs. Drugs 0.50 scores lower; CHM vs. no treatment 0.8 scores lower), and enhance body immunity, with an average increase of 5.26% in CD4 T lymphocytes percentage and lower of 14.64ng/L in serum IL-6 level.However, there was significant clinical heterogeneity among the included trials in this review.We had conducted subgroup meta-analysis according to the different types of virus infection, different disease stages after virus infection, the different TCM treatment principle (e.g.replenishing qi/blood/yin/yang), and different treatment duration, but none of them could explain the source of heterogeneity.This indicated that the heterogeneity may induce by complex factors.Therefore, the evidence we provided was only of a small amount of CHM with tonifying property to post-viral fatigue, and the reliability of the results needed further research and discussion.
Based on the existing TCM syndrome score, a total of 15 trials significantly reduced fatigue compared to the control group, with a maximum lower of 1.73 scores and an average lower of 0.59 scores (CHM vs. Drugs 0.38 scores lower; CHM plus drugs vs. Drugs 0.58 scores lower; CHM vs. no treatment 0.8 scores lower).There was no significant difference in two trials compared with control group, with a minimum lower of 0.04 scores, and the disease types were chronic hepatitis B and viral myocarditis.
In addition, only four studies reported the adverse events, one of which [32] resulted in abnormal liver function.Although there was no difference concerning the incidence of adverse events between groups, safety of CHM in treating post-viral fatigue was still uncertain due to the insufficient evidence.

Limitations
Most of the included trials had methodological limitations, 26.32% of the trials failed to provide the methods for random sequence generation, only two trials described the blinding and one of them used [32] concealment of allocation.Therefore, all of these methodological deficiencies lead to bias.
At the same time, as mentioned above, five viral infectious diseases and 18 CHM preparations with different compositions were included in this review, there was great clinical heterogeneity among the trials.We included 5 kinds of virus infectious diseases.According to the route of transmission, the virus could be grouped into respiratory tract transmission virus, digestive tract transmission virus, contact transmission virus and blood body fluid transmission virus.And according to the status of virus infection, it also could be divided into virus negative but the body still having persistent fatigue (e.g.Long COVID, chronic viral myocarditis) and virus positive, fatigue and virus having a certain correlation (e.g.chronic hepatitis B, AIDS).Therefore, viruses invaded the human body in different ways, different infection states, resulting in high heterogeneity among studies.
In terms of interventions, modern medicine mainly used antiviral drugs in the treatment of virus-related fatigue.However, TCM was characterized by syndrome differentiation and treatment.Therefore on the basis of the treatment principles of supplementing qi, blood, yin, and/ or yang, we usually added or subtraction on basic prescriptions depending on the patients, which leaded to the diversification of prescriptions.It was also the reason for the large heterogeneity among clinical trials.
In addition, the main outcome measurement tool used in this review was the TCM syndrome scale, which might cause bias due to the subjective evaluation criteria.Only two included trials used internationally recognized fatigue scale, most of the remaining trials used TCM syndrome score (which contained scores for fatigue) to assess the improvement of clinical symptoms.TCM syndrome score is a commonly used scale in China, which is guided by TCM syndrome differentiation to evaluate the efficacy of TCM in improving symptoms and signs.In this study, we used the score for evaluating fatigue level in the scale as the primary outcome.Its advantage is that it is highly relevant to the diagnosis of TCM.But we have to admit that this scale lacks a unified evaluation standard, which can not measure the fatigue from multiple dimensions as a whole.We suggest that future researchers try to use internationally recognized outcome measurements as much as possible.*The risk in the intervention group (and its 95% confidence interval) is based on the assumed risk in the comparison group and the relative effect of the intervention (and its 95% CI).CI: confidence interval; MD: mean difference GRADE Working Group grades of evidence High certainty: we are very confident that the true effect lies close to that of the estimate of the effect.
Moderate certainty: we are moderately confident in the effect estimate: the true effect is likely to be close to the estimate of the effect, but there is a possibility that it is substantially different.Low certainty: our confidence in the effect estimate is limited: the true effect may be substantially different from the estimate of the effect.
Very low certainty: we have very little confidence in the effect estimate: the true effect is likely to be substantially different from the estimate of effect.

Implications for clinical practice
Subgroup meta-analysis did not reveal any significant influence of factors such as syndrome differentiation, types of viral infection and duration of treatment in the category of CHM vs. drugs.
This review found that Radix Astragalus 10~50g, Radix Salvia miltiorrhiza 6~20g, Radix Ophiopogon 6~15g and Poria cocos 6~10g were the most frequently used herbs for post-viral fatigue.Modern pharmacological research showed that Astragalus promoted the development of immune organs, enhanced mucosal immune function, increased the quantity and phagocytic capacity of innate immunity, promoted the maturation and differentiation of acquired immunity cells, and improves the expression of antibodies in acquired immunity [50].Tanshinone IIA could improve microcirculation and participate in the development and activation of immune cells [51].In TCM theory, Astragalus and Salvia miltiorrhiza nourished the human body from the perspective of Qi and blood respectively to improve chronic fatigue.Through long-term clinical verification, the efficacy had been widely recognized.Ophiopogonin D and carboxymethyl-pachyman through enhanced exercise endurance, reduced lactic acid accumulation and increased glycogen reserve in mice to produce great anti-fatigue effect [52,53].

Implications for future research
Chronic fatigue is a prominent symptom after virus infection, causing psychological and physical harm to patients, seriously interferes with people's life.However, in a review of 19 studies, we found that most of the existing studies only evaluated fatigue as one of the many symptoms after viral infection using the TCM syndrome scale.The subjectivity of evaluation is strong, lacking of objective quantitative analysis of fatigue.Therefore, future clinical trials should focus on the symptom of fatigue and use authoritative fatigue measurement tools (e.g.Chalder fatigue scale [27]) to evaluate.This will contribute to explore insight into the effectiveness of CHM in improving post-viral fatigue.
In addition, this review is an overall evaluation of the efficacy of all existing CHM with tonifying property in the treatment of post-viral fatigue, but limited by the number of existing trials, no reliable results have been obtained.However, taking this study as an opportunity, there are still many ideas that can be further explored.It includes a individual evaluation of the efficacy of CHM for symptoms caused by a specific type of virus (e.g.respiratory viruses, gastrointestinal viruses.etc)and a separately evaluation of CHM for fatigue in different virus infection status (e.g.virus continued positive or has turned negative).Therefore, with the increase of the number of trials in the future, in-depth research can be carried out for a certain direction.
At the same time, from the perspective of methodology, it is also necessary for researchers to carry out more high-quality RCTs with multiple centers and large samples.In the research process, the random sequence generation, the concealment of allocation and blinding should be strictly implemented, and the shedding situation of patients, adverse events and economic costs should be definite clarified.In addition, based on the recurring nature of chronic fatigue, future studies with longer follow-up times should be conducted to confirm the long-term efficacy and safety of CHM for post-viral fatigue.

Conclusion
Current very low quality evidence showed that the participation of CHM can improve the symptoms of post-viral fatigue and some immune indicators.However, the safety of this complementary alternative therapy remains unknown.Large sample, high quality multi-center randomized controlled trials are needed to be conducted in the future.
Finally, we included 19 trials through full-text screening.The PRISMA 2020 flow diagram for literature screening is shown in the Fig 1.

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Lack of allocation concealment and blinding method indicate high risk of selection and detection bias b .Wide confidence intervals and small sample size indicate less imprecision of the results c .Large I 2 value indicate obvious heterogeneity among included trials d .High probability of publication bias https://doi.org/10.1371/journal.pone.0300896.t006 China Network Knowledge Infrastructure (CNKI), China Scientific Journals Database(VIP), Wan Fang Database, Chinese Biomedical Literature Serving System (SinoMed), PubMed, the Cochrane Central Register of Controlled Trials (CENTRAL), the US National Institutes of Health Ongoing Trials Registry, The Chinese Clinical Trial Registry and the World Health Organization International Clinical Trials Registry platform from their inception to 19 th November 2023.